Abstract：Studies show that the carbon isotopic characteristics of the components of chloroform bitumen “A” in Jurassic hydrocarbon source rocks were mainly affected by parent materials and sedimentary environments in Jurassic in south Qiangtang basin. For the components of chloroform bitumen “A” in Xiali Formation hydrocarbon source rocks, the carbon isotopic compositions are usually relatively heavy, while for the components of chloroform bitumen “A” in Buqu Formation hydrocarbon source rocks, the carbon isotopic compositions are usually comparatively light. In addition, the carbon isotopes commonly show reverse phenomenon, and the reversal of δ13C in Xiali Formation source rocks finds expression in the sequence of saturated hydrocarbons < non-hydrocarbons < aromatics < asphaltenes, mainly controlled by organic matters, whereas the reversal of δ13C in Biqu Formation source rocks finds expression in the sequence of non-hydrocarbon>asphaltenes> saturated hydrocarbons> aromatic hydrocarbons, mainly related to biological degradation.